The ask bar under the page on the owner page takes a change in plain words, such as "Add our Saturday hours, 9 to 2", and miow makes it.

1. Type the change into the bar.
2. Choose where it applies: in the block you are in, On this page, or Across the site.
3. Press Make the change.

When it is done the bar says Done., with Undo and Keep it. Undo puts the site back as it was before; Keep it leaves the change in place. Either way the change is in History, where it can be undone later; see Undo a change.

Can it move pages in from another website?

Yes. An address pasted into the bar turns the button into Replace this site with it; see Move an existing site.

Does a wiki have one?

No. A wiki's pages are written one at a time; see Write a wiki.